Adhesion is always a factor with aged surfaces
One of the problems with painting over unknown and older surfaces is the lack of adhesion. It's important for subsequent layers to adhere to what's already there else the top coat will peel. At 200 mph, you'd be amazed what lousy adhesion will do.
The last post was correct. Clean it thoroughly so no grit is left on the surface. Using DX330, wipe in one direction only, and wear rubber gloves because DX330 is not good for your skin.
Prepping a surface for primer or paint is not like waxing your Honda. Your rag should accumulate dirt and then be discarded when it's full. Pour the cleaner onto the rag rather than allow the rag to deposit trash back into the can.
Personally, I would scuff sand the old stuff so the new primer has something to bite into. Wet sand with 3M 320 grit paper should help. You won't get a great chemical adhesion due to the age of the primer but you should get a mechanical bond.
After a final wipe with DX330, use a tack cloth to pick up any final particles. Once again, wipe in one direction only.
Most good paint shops can tell you what's already there and make a good recommendation. Study the process, try to work in as clean an environment as possible, and my all means, wear a good respirator or better yet, wear a fresh air respirator that draws in air from outside the booth.
Read the labels. Allow the chemistry to scare the *&^%$ out of you so you protect your hands and lungs. You only get two of each.